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Exam 1-solutions

# Exam 1-solutions - Version 138 Exam 1 Mccord(50970 This...

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Version 138 – Exam 1 – Mccord – (50970) 1 This print-out should have 31 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 10.0 points The higher the energy of electromagnetic ra- diation, the 1. greater its mass. 2. lower its frequency. 3. shorter its wavelength. correct 4. higher the velocity of light. 5. longer its wavelength. Explanation: For electromagnetic radiation, the energy of radiation is related to its frequency by the equation E = h ν , where h is Planck’s constant, ν = c λ , and c is the speed of light in a vacuum (also a constant). Thus, the equation that relates energy to wavelength for electromagnetic radiation is E = h c λ As energy increases, ν (frequency) must also increase, and λ (wavelength) must decrease. 002 10.0 points The 7 g orbital for hydrogen looks quite com- plex. How many nodal planes are there in a 7 g orbital? 1. five 2. six 3. three 4. two 5. four correct 6. seven 7. one Explanation: Nodal planes = value of quantum number which is 4 for g . 003 10.0 points Note: “same intensity” means the same num- ber of photons per second. We conduct an experiment by shining 500 nm light on potassium metal. This causes electrons to be emitted from the surface via the photoelectric effect. Now we change our source light to 450 nm at the same intensity level. Which of the following is the result from the 450 nm light source compared to the 500 nm source? 1. Fewer electrons would be emitted from the surface. 2. More electrons would be emitted from the surface. 3. No electrons would be emitted from the surface. 4. The same number of electrons would be emitted, but they would have a higher velocity correct 5. The same number of electrons would be emitted, but they would have a lower velocity Explanation: 500 nm light has more energy than than the work function of potassium due to the fact that electrons were emitted. Therefore 450 nm light, which is higher in energy than the 500 nm light, will also emit electrons. The number of electrons emitted must be the same because the intensities (photons/s) are the same. However, the higher energy photons from the 450 nm light would yield electrons with a higher kinetic energy and therefore a higher velocity. 1 2 mv 2 = - Φ

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Version 138 – Exam 1 – Mccord – (50970) 2 004 10.0 points The n and quantum numbers of the last electron of an element are n = 4 and = 3. The element is 1. an f -transition metal. correct 2. a representative element. 3. a nonmetal. 4. a d -transition metal. 5. a noble gas. Explanation: Where n = 4 and = 3, 4 f electrons are filling. These are the f -transition metals. 005 10.0 points Which of the following groups of atoms is correctly arranged in order of decreasing first ionization energy? 1. In > Ge > P 2. Ge > As > Se 3. Rb > K > Na 4. Cl > Br > I correct Explanation: First ionization energy increases as one moves from left to right on a given row and increases from bottom to top as one moves up a given family.
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Exam 1-solutions - Version 138 Exam 1 Mccord(50970 This...

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